Electrophotographic (EP) printers are useful for producing printed images of a wide range of types. Printers print on receivers (or “imaging substrates”), such as pieces or sheets of paper or other planar media, glass, fabric, metal, or other objects. In the EP process, a photoreceptor is uniformly charged and imagewise discharged. Electrified charging rollers (“roller chargers”) are commonly used to charge the photoreceptor, e.g., as discussed in U.S. Pat. No. 7,454,154 to Matsumoto et al. However, toner, paper fibers, and other contaminants can adhere to the photoreceptor and transfer to the roller charger. Over time, these contaminants can reduce the effectiveness with which the roller charges the photoreceptor, or cause non-uniform charging of the photoreceptor, thereby reducing image quality.
Some printers use electrical bias to drive charged contaminants off a roller charger. For example, the CANON M50 printer reverse-biases the charge rollers to drive contaminants onto the photoreceptor, from which they are cleaned by a photoreceptor cleaner. Other schemes include the charger roller as part of a customer-replaceable unit in a printer. The roller is not cleaned, so the customer must replace the unit when the roller contamination reaches unacceptable levels.
Cleaning blades or skives are sometimes used to clean members in EP printers. However, many roller chargers are foam, fur, or another member with a non-rigid surface. For example, U.S. Pat. No. 7,630,664 to Ozawa et al. describes a charging roller with an elastic outer layer. Such compliant or textured roller surfaces are not cleaned effectively by blades. Furthermore, hard-surfaced roller chargers can be damaged by blade cleaners if contaminants become lodged between the blade and the roller. Also, cleaning can produce mechanical wear on a charging roller, and it is desirable to reduce wear to increase the useful life of the roller charger. Similar wear on other components of a printer is described in U.S. Pat. No. 6,836,630 to Owen et al. Additionally, compliant cleaning elements can themselves be deformed or damaged during cleaning. Ozawa '664 describes a compliant cleaning element movable between a more-compressed position and a less-compressed position. However, this scheme is not particularly useful for compliant charge rollers. U.S. Pat. No. 5,873,019 to Mizuishi describes cleaning and disengaging a roller charger. However, this scheme can reduce throughput, since printing cannot be performed while the charger is disengaged.
There is, therefore, an ongoing need for an improved cleaning apparatus for a roller charger that cleans effectively without reducing throughput and without requiring regular replacement.